Circuit interrupter



Sept. 27, 1932.

M. B. TASKER 1,879,958

CIRCUIT INTERRUPTER Filed June 29, 1929 Patented Sept. 27, 1932 UNITED STATES PATENT OFFICE MAURICE B. TASKER, OF DANVERS, MASSACHUSETTS, ASSIGNORTO CON DIT ELECTRICAL MANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS, A CORPO- RATION OF MASSACHUSETTS CIRCUIT INTERRUPTER Application filed June 29,

This invention relates to alternating current electric switches and circuit interrupters and to a method and apparatus for eXtinguishing the alternating-current circuitinterrupting are. I

It has been proposed to interrupt an electric circuit by drawing a circuit interrupting are between separable arcing members and passing the are into a plurality of closelyspaced conducting plates whereby to divide the single long are into a plurality of short arcs which are more readily extinguished by the cold plates, the number of plates being such that the sum of the dielectric strengths of the normally insulating medium between the piates is at least equal to the normal potential of the circuit so that the arcs cannot be re-formed after they have gone out. In some cases the short arcs have been rotated about and in contact with the plates.

In order to insure the greatest effectiveness of the stack of plates, the potential drop between the plates s'hould be uniform for, if the potential drop that is impressed across any two adjacent plates by the potential of the power source is greater than the dielectric strength of the arc zone, an arc will form between the plates. In order to provide an approximately uniform potential gradient between the plates, it has been proposed to utilize an electrostatic shield for the plates. Such shielding means, however, is objectionable in that it necessitates extra apparatus and circuit connections and requires additional insulation and special design of the parts of the interrupter.

It is an object of the present invention to provide an approximately uniform potential gradient between the arc plates in such manner as to avoid the necessity for an electrostatic screen or other special apparatus.

Specifically this object is carried out by varying the electrostatic capacities between the plates, either by varying the areas of the plates or by varying the spacing therebetween in a manner. best adapted for this purpose.

A further object is generally to improve upon circuit interrupters and circuit interrupting methods.

Fig. 1 is a diagrammatic representation of 1929. Serial No. 374,783.

a circuit interrupter wherein the areas of the arc plates are varied in accordance with this invention.

Fig. 2 is a view similar to Fig. 1, but wherein the spacing between the arc plates is varied.

Fig. 3 is a curve representing the potential distribution across a stack of arc plates that is not provided for potential equalization therebetween.

Fig. 4 is a curve showing the theoretically uniform potential equalization provided with the present invention.

As herein shown, the circuit interrupter has the fixed contact member 10 and the movable pivoted contact member 12, both contact members being connected to the circuit by the conductors 14 and 16. The movable contact member 12 is adapted to move away from the contact member 10 into some position as indicated by the dotted lines and to draw an arc therebetween.

A stack of arc plates is located above both of the movable contact members and in line with the zone of the arc therebetween so that the are drawn between said contact members is caused to move upwardly into the stack, either by the natural upward movement of the arc due to thermal causes or by magnetic means, not herein shown. The stack of conducting arcing plates includes the end plates 18 and 20, and a plurality of spaced and insulated intermediate plates 22. The plate 18 is connected with the contact member 10 while the plate 20 is connected by a shoe 24 with the movable contact member 12 when the latter is in switch-open position. Thus, the stack is included in series with the circuit to be interrupted. The single are drawn between the separable contact members is thus directed into the stack and is caused to be broken up into a plurality of short arcs which are located between and have their seats on the plates. If desired, means as the solenoids 26, which are located between and connected with adjacent plates and thus in series with the stack of plates, may be provided to cause the short arcs to rotate about and in engagement with the cold plates.

With the above arrangement, it is desirable to have the potential difference between confronting plates uniform throughout the stack.

If it is not made uniform the potential difference usually is greatest at the end plates and least at the middle plates. Thus, after the arc has gone out and potential is impressed across the stack, the potential difference across the end plates may be suflicient to break down the dielectric strength of the medium therebetweenr This places an increased potential across the next plates of the series so that a progressive break down is caused; and the arc is reformed.

' In accordance with the present invention, the plates of the stack are so i'arrangcd that the potential gradient between them is approximately uniform. Where the electrostatic capacities. between the plates are all uniform the potential gradient is steepest at the end plates 18 and 20 and is least steep at the middle plates, as illustrated by the curve of Fig. 3. 7

In accordance with this invention, the electrostatic capacities between the plates are so arranged that the capacities are greatest where the potential gradient is normally greatest, as at the end plates, and is least where the potential gradient is the least, as at the middle of the stack.

The variation in electrostatic capacities can be obtained in two Ways. In Fig. 1, those plates 22 of the stack that are nearest the end plates 18 and 20 are larger in confronting area than are the plates in the middle of the stack. Consequently, the electrostatic capacity of the plates having the greatest area is the greatest. Thus the potential gradient between ,such plates is less than the potential gradient between those plates having the least confronting areas. The relation between the areas is chosen so that the potential gradient is approximately a straight line, as shown in Fig. 4.

In Fig. 2, the variation in electrostatic capacities is provided by varying the spacing between the plates. The plates 22 nearest the end plates 18 and 20 are closer together than those plates in the middle of the stack; and the spacing between the plates is so graduated that the potential gradient is uniform throughout, as illustrated in Fig. 4.

I claim:

1. A circuit interrupter having a stack of spaced and insulated arcing plates between which circuit interrupting arcs are supported, the inherent electrostatic capacities of said plates being different in such manner as to provide uniform potential differences therebetween.

2. A circuit interrupter having a stack of spaced and insulated arcing plates between which circuit interrupting arcs are supported, the inherent electrostatic capacities of said plates being difierent in such manner as to provide uniform potential differences therebetween, and means to rotate the arcs about the confronting surfaces of said plates. 3. A circuit interrupter having a stack of spaced arcing plates between which circuit interrupting arcs are supported, the end plates of the stack being connected with the circuit to be interrupted at the time of circuit interruption and the inherent electrostatic capacities of said plates being different in such manner as to provide a uniformpotential difference between said plates.

4. A circuit interrupter having a stack of spaced arcing plates between which circuit interrupting arcs are supported, the end plates of the stack being connected with the circuit to be interrupted at the time of circuit interruption and the inherent electrostatic capacities of said plates being different in such manner as to provide a uniform potential diiference between said plates, and means to rotate the arcs about said plates.

5. A circuit interrupter having a stack of spaced arcing plates between which circuit interrupting arcs are supported, and means to connect the end plates of the stack to the circuit at the time of circuit interruption, the inherent electrostatic capacities between said plates being less between the middle plates of the stack than between the end plates of the stack.

6. A circuit interrupter having a stack of spaced arcing plates between which ciruit interrupting arcs are supported, and means to connect the end plates of the stack to the circuit at the time of circuit interruption, the inherent electrostatic capacities between said plates being less between the middle plates of the stack than between the end plates of the stack, and means to rotate the arcs about said plates.

7 A circuit interrupter having a stack of spaced arc plates between which circuit interrupting arcs are supported, and means to connectthe end plates of the stack to the circuit at the time of circuit interruption, the spacing between the middle plates of the stack being greater than the spacing between the end plates of the stack.

8. A circuit interrupter having a stack of spaced arc plates between which circuit interrupting arcs are supported, and means to connect the end plates of the stack to the circuit at the time of circuit interruption, the spacing between the middle plates of the stack being greater than the spacing between the end plates of the'stack, and means to rotate the arcs about said plates.

9. A circuit'interrupter having a stack of spaced arc plates between which circuit interrupting arcs are supported, and means to connect the end plates of the stack to the circuit at the time of circuit interruption, said plates having confronting surfaces of uniform area and the spacing between the middle plates of the stack being greater than the spacing between the end plates of the stack.

10. A circuit interrupter having a stack of spaced are plates between which circuit interrupting arcs are supported, and means to connect the end plates of the stack to the circuit at the time of circuit interruption, said plates having confronting surfaces of uniform area and the spacing between the middle plates of the stack being greater than the spacing between the end plates of the stack, and means to rotate the arcs about said plates.

11. A circuit interrupter having separable contact members between which an electric arc is adapted to be drawn, a stack of spaced arcing plates located in proximity withthe arc zone and adapted to receive the arc, which are enters the spaces between said plates and forms a plurality of short arcs therein, the end plates of said stack being connected in series with the circuit to be interrupted and the inherent electrostatic capacities between said plates being different in such manner that the potential difierences between confronting plates is uniform.

12. A circuit interrupter having separable contact members between which an electric arc is adapted to be drawn, a stack of spaced arcing plates ,cated in proximity with the arc zone and adapted to receive the are, which are enters the spaces between said plates and forms a plurality of short arcs therein, the end plates of said stack being connected in series with the circuit to be interrupted and the inherent electrostatic capacities between said plates being different in such manner that the potential differences between confronting plates is uniform, and means to rotate the arcs between said plates.

13. A circuit interrupter having separable contact members between which an electric arc is adapted to be drawn, a stack of spaced arcing plates loca ed in proximity with the arc zone and adapted to receive the are, which are enters the spaces between said plates and forms a plurality of short arcs therein, the end plates of said stack being connected in series with the circuit to be interrupted and the electrostatic capacities between said plates being different in such manner that the potential differences between confronting plates is uniform, the plates being differently spaced and the spacing between the plates in the middle of the stack being greater than the spacing between the plates at the ends of the stack.

14. A circuit interrupter having separable contact members between which an electric arc is adapted to be drawn, a stack of spaced arcing plates located in proximity with the are zone and adapted to receive the are, which are enters the spaces between said plates and forms a plurality of short arcs therein, the end plates of said stack being connected in series with the circuit to be interrupted and the electrostatic capacities between said plates being different in such manner that the potential differences between confronting plates is uniform, the plates being differently spaced and the spacing be tween the plates in the middle of the stack being greater than the spacing between the plates at the ends of the stack, and means to rotate the arcs between said plates.

15. A circuit interrupter having a stack of spaced and mutually insulated arcing plates between which circuit interrupting arcs are supported, said plates having graded confronting areas, whereby to vary the electrostatic capacity between the several plates in a determined manner.

16. A circuit interrupter having a stack of spaced and mutually insulated arcing plates between which circuit interrupt-ing arcs are supported, and means to connect the end plates of the stack in the circuit at the time of circuit interruption, said plates having unequal confronting areas, whereby to vary the electrostatic capacities therebetween in a determined manner.

17. A circuit interrupter having a stack of spaced and mutually insulated arcing plates between which circuit interrupting arcs are supported, and means to connect the end plates of the stack in the circuit at the time of circuit interruption, said plates having unequal confronting areas, whereby to vary the electrostatic capacities therebetween in a determined manner, and the arrangement of the plates being such that the plates having the least area occupy a position intermediate those having greater areas.

18. A circuit interrupter having a stack of spaced and mutually insulated arcing plates between which circuit interrupting arcs are supported, and means to connect the end plates of the stack in the circuit at the time of circuit interruption, said plates having uniformly graded confronting areas, the plates having the greatest areas being disposed at the ends of the stack and the plates having the least areas being disposed in the center of the stack, whereby to provide a uniform potential difference between confronting plates.

In testimony whereof, I have signed my name to this specification.

MAURICE B. TASKER. 

